In heat exchange equipment exposed to direct and indirect sources of heat, the temperatures require the protection of the surfaces of equipment by a layer of refractory. As insulation and physical protection from deteriorating chemicals, refractory, more often than not, has dimensional changes which differ significantly from the dimensional changes of the material which it protects. This single condition may be only one of the factors which threaten support of the refractory by the protected surfaces.
Many different forms of projections have been welded to substrate surfaces to which it is necessary that refractory be applied as a protective layer. Protruding studs have been welded to these surfaces. Also, clips, anchors, and metal straps have been attached in various ways and in various configurations to substrate surfaces in attempts to lock on to the refractory material during the variable conditions to which the combination is exposed. Unfortunately, the refractory eventually falls out of its position among these projections, necessitating expensive maintenance and replacement.
The art has advanced to providing a matrix of metallic fibers, or strands mixed with the refractory. It has been recognized that a bond between the contacts of the fibers/strands with each other, and the fibers/strands with the substrate surface will substantially lengthen the support of the refractory by the substrate surface. However, a satisfactory process for high-temperature brazing the metal fibers/strands to each other, and the fibers/strands to the substrate, has eluded those skilled in this art. The difficulty is fundamentally in holding whatever bonding material is required close enough to the junction of metal fibers/strands and fibers/strands and substrate surface while the surfaces to be bonded are maintained clean enough to enable a dependable bond to be formed. Heretofore, all vehicles utilized to hold the bonding material to the strand-to-strand junctions, and strand-to-substrate junctions have been evaporated to leave residues which have created a low-quality bond at the junctions, or they have not held the brazing powder in place. From the foregoing description of the present art, a mechanism is required which will hold bonding material on the surfaces of metal strands/fibers until a bond of the strands/fibers to each other, and the strands/fibers to the substrate is completed without loss of bonding quality.